Enhancing Internet behavioral weight loss programs with portion controlled foods (Webber, PI) Obesity is arguably the most pressing public health concern in the U.S. Currently two-thirds of U.S. adults are overweight or obese. Excess weight is associated with increased risk of chronic diseases including coronary heart disease, Type 2 diabetes, and some cancers. Modest weight loss, even as little as 5-10% of baseline body weight, can reduce chronic disease risk. Both Internet and face-to-face behavioral weight loss programs produce clinically significant weight loss results. Research has shown that adding structure to a low-calorie diet increases adherence and weight loss. Therefore one possible enhancement to weight loss involves bringing together behavioral programs with portion controlled foods (PCD). The Overall Goal of this project is to develop, deliver, and evaluate four different weight loss interventions. To achieve this goal, the following specific aims are proposed: 1. To evaluate the effectiveness and cost effectiveness of four different weight loss intervention approaches: (1) face-to-face program alone (2) face-to-face program supplemented with six months of PCD (3) Internet program alone and (4) Internet program supplemented with six months of PCD, for producing weight loss and improvements in metabolic syndrome biomarkers at 3, 6, and 12 months. 2. To evaluate each of the four different intervention approaches for differences in the behavioral mediators of self-monitoring, social support, self-efficacy, and motivation at 3, 6, and 12 months. Participants will be randomized to one of four groups for the six month intervention which will be followed with a six month follow-up period. Primary and secondary outcomes including weight, abdominal and waist circumferences, dietary intake, physical activity, resting blood pressure, blood lipids, fasting glucose and insuli, HbAlc, hs-crp, and psychosocial variables will be taken in the clinic at baseline, 3, 6, and 12 months. The study will be powered using a non-inferiority trial design to demonstrate that the Internet plus PCD intervention is clinically at least as effective as the face-to-face alone intervention over six months of treatment.